Switches have long been used in electrical circuit designs to isolate a portion of an electrical circuit. In its simplest form, a switch operates to allow a signal to pass from an input terminal to an output terminal in a “closed” position and to prevent the signal from passing from the input terminal to the output terminal in an “open” position.
In the microwave and mm-wave frequency range, switches are used in instrumentation, communications, radar, fiber optic and many other systems that require high-frequency switching. For example, a switch can be used for pulse modulation, port isolation, transfer switching, high-speed switching, replacement of mechanical parts and other switch applications.
There a number of commercially available high-frequency switches on the market today. However, these switches have all failed to simultaneously obtain high switch isolation greater than 15 dBm, high power handling above 24 dBm and low insertion loss of a fraction of a dB from DC to mm-wave frequencies. For example, high-frequency switches employing field-effect transistors (FETs) typically are unable to handle high frequencies in the mm-wave range and/or high power above 24 dBm. In the alternative, FET-based solutions may have high insertion loss. In addition, waveguide-based switches are difficult to integrate and lack the required bandwidth coverage to DC. Furthermore, coupling-based diplexers typically have poor isolation and high insertion loss at the cross-over frequency.
Therefore, what is needed is a switch capable of achieving high switch isolation, high power handling and low insertion loss from DC to mm-wave frequencies.